Internal combustion engines typically use only a portion (for example, approximately 31% to 38% in some cases) of the energy in supplied fuel due to wasted heat, friction, incomplete combustion, and others such factors. In addition, approximately 3-17% of the supplied fuel energy may be used to maintain the engine operation during standby and another 1-2% may be used to operate accessories. Therefore, it may be beneficial to utilize waste energy, typically in the form of thermal and chemical energy, to improve overall fuel efficiency.
One approach to utilize the waste energy is to arrange a solid oxide fuel cell (SOFC) in an exhaust system of an internal combustion engine. For example, U.S. Patent Application No. 2004/0177607 describes an internal combustion engine with a SOFC in an exhaust system. This reference also describes oxidative catalysts disposed upstream and downstream of the SOFC within the exhaust system. The upstream oxidative catalyst is used to reform fuel for the SOFC, and the downstream oxidative catalyst is used to treat any unoxidized or partially oxidized exhaust constituents not consumed by the SOFC. However, such a system may still waste not utilize energy efficiently. For example, heat from oxidative reactions occurring in the oxidative catalyst may be lost in such a system.
The inventors herein have realized that waste energy may be more efficiently utilized by an apparatus comprising an internal combustion engine, an exhaust system for conducting exhaust emitted by the engine, and a catalytic device associated with the exhaust system, wherein the catalytic device comprises a catalytic conversion portion and a fuel cell portion. Such an apparatus may allow heat from chemical reactions in the catalytic conversion portion to assist in heating the fuel cell portion of the catalytic device, and may offer other benefits as well.